The present invention is directed to impellers, and more particularly to an impeller manufactured as single piece having the optimal manufacturability, lowest cost, most efficient design, and lowest material usage to provide superior capabilities with respect to cost without sacrificing durability.
Impellers have been around for many years as a tool for creating a flow of either a gas or a liquid. Common uses for impellers have been for cooling mechanical or electrical devices by creating a flow of a cooling medium. There are two main design considerations for an impeller: the cost of manufacture and durability in the desired environment.
An example of an impeller known in the art is that disclosed in U.S. Pat. No. 5,478,206 to Prahst. The Prahst patent discloses an impeller having a guide ring for a radial fan made to direct a flow of a medium directly onto an object. While the impeller blades for the radial fan in Prahst can be made in one piece, the design lacks the essential element of a rear support plate. To direct the flow of fluid out radially from the impeller, one would need to add a rear support plate or a frame to direct the flow. The addition of a rear plate typically involves costly secondary processing and assembly. The present invention addresses deficiencies involving radial output fans while maintaining the benefit of one-piece manufacture.
The present invention relates to an impeller primarily used with AC motors or blowers. However, the impeller of the present invention may easily be adapted to any impeller that can be made by the injection molding process or any processes that involve male and female reusable mold halves which shape a deformable material. The common material used to make impellers has been synthetic materials, such as thermoplastics, where the service conditions allow. The prior art method for producing impellers out of thermoplastics involved the injection molding of impellers in two pieces.
Once the two halves of the prior art injection molded impeller were molded, the two halves were removed and inspected. If the parts proved to be of sufficient quality, the two halves undergo a second processing step of friction welding. Friction welding involves the heating of a thermoplastic part through friction, as the name implies. Friction is generally created by spinning a first half of the part, which is anchored to a large rotating mass, and forcibly pressing the first half against the second half of the part which mounted firmly in place. The movement of the two plastic parts against each other causes intense heat from the friction between the touching surfaces. The intense heat causes the two components to melt, flow and knit together.
The disadvantages of friction welding are numerous. The first disadvantage of friction welding is that it excludes many intricate and delicate parts from being welded together. Secondly, the parts are limited to certain materials that are capable of forming strong friction welds. Additionally, the parts must be heavier, using more materials and thus at a greater cost to endure the severe stresses associated with the process. Finally, the friction welding process involves a secondary step, which involves setup and inspection to ensure a quality part.
An improvement in the art over friction welding in manufacturing the impeller discussed above involves sonic welding the two-piece impeller together. While the sonic welding procedure still involved the same additional costs and shortcomings, the sonic welding process allows for the use of more intricate designs and a marginal reduction in part weight.
Sonic welding involves the use of sound, or more specifically a tuned vibration, to heat up and join the parts together. With sonic welding, one half of the part is rigidly affixed to a mount and the second half is affixed to a moveable section which undergoes an intense cyclic vibration. The parts are then moved in contact with each other and the friction from the rapidly vibrating half in contact with the stationary half causes the thermoplastic at the point of contact to soften and flow. It is common practice to add various features to parts that concentrate friction along certain points of the weld line to improve the weld strength.
Sonic welding also includes many inherent deficiencies, such as extra cost, time and expense in manufacturing the impeller. Even with the use of specific features to concentrate friction, there can still be a problem involving weakness and potential failure at the weld line due to poor knitting of the plastic between the two parts.
The present invention addresses and corrects all the deficiencies of the earlier manufacturing methods while producing an impeller with superior properties and cost savings.
Accordingly, it is an object of the present invention to provide a onepiece impeller that has superior durability. It is another object of the present invention to provide a one-piece impeller that reduces the complexity involved with manufacturing. It is yet another object of the present invention to provide a one-piece impeller with a synthetic material that achieves the same performance as traditional two-piece impellers. It is a further object of the present invention to lower the cost of manufacturing an impeller in combination with superior performance capabilities. It is still a further object of the present invention to provide a one-piece impeller having superior stability and reduced mass. Another object of the present invention is to provide a one-piece impeller with reduced material usage and less scrap. Furthermore, it is an object of the present invention to reduce the amount of secondary operations in manufacturing the impeller.
The present invention achieves the above-described objectives by providing a one-piece impeller having a plurality of impeller blades, a central hub and an inlet support ring. The impeller of the present invention is preferably made of a stiff synthetic thermoplastic resin that has high durability and allows for ease of processing using machines, such as injection molding machines. This combination has been found to produce an impeller with superior cost and performance capabilities, which also satisfies the need for durability.
The impeller must be constructed from a relatively stiff material, for example, synthetic thermoplastic materials. Most notably, these synthetic thermoplastic materials are engineering resins because of their superior properties and dimensional stability. However, it is envisioned that non-engineering resins or commodity resins, such as olefins, could be used if properly modified with additives or fillers to provide the necessary dimensional stability and physical properties. The material selection for the present invention is much wider without the constrictions placed on the material selection by friction or sonic welding.
The present invention utilizes an improved design for impellers. It has been discovered that incorporating specific design features into the impeller allows the impeller to be injection molded in one step while still retaining, if not easily surpassing, the durability and performance of the prior art impeller. The one-piece impeller design replaces the cumbersome two-piece design that necessitated the secondary operations of molding separate pieces, inspecting the pieces for quality and then friction or sonic welding the components together. Furthermore, the impeller design of the present invention has much improved balance over the prior impeller designs right out of the mold.
Additionally, compatible additives may be added to the synthetic polymer of the present invention. Examples of common additives are stabilizers, fillers and processing aids. The final amount of additives is dependent on the exact polymer used and should be adjusted accordingly.
These and other objects of the present invention will be apparent from a reading of the following detailed description of the present invention.
Various other features, objects and advantages of the invention will be made apparent from the following description taken together with the drawings.